Tie yarn for incandescent bodies and the use thereof

ABSTRACT

The invention relates to an asbestos-free binding yarn for fastening incandescent bodies to burners of incandescent lamps whose incandescent bodies after the fastening are exposed to a flame, wherein the binding yarn consists of a fireproof material, preferably silica yarn. For improving the knotting ability of the yarn it is envisaged that the binding yarn after exposure in the flame has a diameter changed of less that 50% of its original diameter. The subject-matter of the invention is also the use of the binding yarn on an incandescent body for increasing its retention and durability.

FIELD OF THE INVENTION

[0001] The invention relates to an asbestos-free binding yarn forfastening incandescent bodies to burners of incandescent lamps, whoseincandescent bodies are exposed to a flame after fastening, wherein thebinding yarn consists of fireproof material and comprises a finishincreasing the skin friction of the material.

[0002] Apart from the number of sewing stitches with which the bindingyarn is sewn into the incandescent body fabric, wherein as the case maybe, one sews through both layers of fabric if the end of the fabric hoseor bag has been turned up, it is above all the nature of the bindingyarn which is significant for the mechanical durability of anincandescent body on the burner of an incandescent lamp. The selectionof the binding yarn is subject to various criteria. It must be resistantto high temperatures, must retain its textile properties at a hightemperature and become neither hard nor brittle. This is to say a yarnof steel is of no use, and the knot must endure well.

BACKGROUND OF THE INVENTION

[0003] In the past, asbestos yarn was the only binding yarn to be usedwith incandescent bodies. This yarn was enduring at high temperaturesand could be easily knotted. It however has the disadvantageouscharacteristic that it is damaging to health and has therefore beenprohibited in many countries. The disadvantageous properties ofasbestos, in particular the limited usability on account of itsprohibition has led to the search and application of new binding yarns.

[0004] Thus it has been attempted to use cotton yarn which isimpregnated in metal salts, e.g. of rare earths. During the burning-awayof the incandescent body, the cotton burns without any residue and anoxide skeleton in the form of a yarn remains. The skeleton is likewiseenduring at high temperatures and in the original condition the yarn maybe easily knotted. The disadvantageous property lies in the fact thatafter the burning-away of the incandescent body only the oxide skeletonarising from the impregnation salts remains, which has no tear strengthand may not hold the incandescent body on the burner for a long time.This yarn therefore was hardly used in practice.

[0005] Binding yarns based on glass fiber, ceramics, organic materials,e.g. aramide, carbon fibers etc. are also known. The endurance at hightemperature is counted amongst the advantageous properties. However, atthe same time there are also disadvantages. These yarns have such asmooth and such a friction-free surface that they are difficult to knotor the knot easily becomes undone. (A knot only holds on account of thefriction). With a low Tex number there is a low tear strength, poorprocessing ability, e.g. on sewing, cutting, etc.

[0006] Common binding yarns from which the invention proceeds consist ofa glass fiber or ceramic core or a silica core of approx. 0.2 mmdiameter enveloped with cotton of stack fibers according to theInternational patent application PCT/GB92/00432 so that there results atotal diameter of approx. 0.5 mm.

[0007] These have a silica yarn core enduring at high temperatures andmay be knotted since the smooth silica yarn is sheathed to excess withnon-smooth cotton yarn, which overcomes the smoothness and renders theknot lasting. They are tear-resistant and may be easily processed. Thedisadvantage with these is the fact that the incandescent body which isoriginally rigidly attached to the burner, after the burning-away of theincandescent body, is seated loosely on the burner, by which means themechanical durability on the burner is reduced. The initially tight knotis likewise loose after the burning-away of the wrapped winding. Themanufacture is effected in an expensive DREF machine and the yarn istherefore very expensive. Furthermore, it is often the case that as aresult of operational trouble the core is no longer co-conveyed, but theproduction continues to run. Such errors may not however be recognizedby optical control so that after burning-away the binding yarn hasdisappeared and the incandescent body falls down.

[0008] Finally instead of a binding yarn, a round metal clip accordingto U.S. Pat. No. 5,116,220 and U.S. Pat. No. 5,639,231 are used. Themetal clip is sewn into the incandescent body at the height at which thebinding yarn would have been sewn in. This metal clip is enduring athigh temperature and is operationally friendly since the user does notneed to tie any yarn. The connection between the incandescent body andthe burner does not have the same compactness, as is the case with thebinding yarn. The incandescent body does not perfectly contact theburner (see U.S. Pat. No. 5,639,231). The lack of retention of theincandescent body on the burner is the price to pay for the operationalfriendliness of the metal clip.

[0009] It is therefore the object of the invention to provide anoperationally friendly yarn which may be easily knotted and furthermoreincreases the application duration and durability of an incandescenthood subjected to knocks and impacts.

SUMMARY OF THE INVENTION

[0010] An asbestos-free binding yarn for fastening incandescent bodiesto burners of incandescent lamps, whose incandescent bodies are exposedto a flame after the fastening, wherein the binding yarn consists of afireproof material and comprises a finish increasing the skin frictionvalue of the material, achieves this object in that the binding yarn hasa diameter change after exposure in the flame of less than 50% of itsoriginal diameter. It has been surprisingly found out that the reductionof the diameter shrinkage on burning-away significantly contributes tothe increase in the life expectancy of the incandescent hood. In trialswith which the burnt-off incandescent hood is subjected to an impactloading or oscillation loading, an increase of the life expectancy ofthreefold with respect to incandescent hoods which were fastened withyarn according to the state of the art was ascertained. In this context,yarn is to be understood as any ductile one-dimensional body, thread,yarn or tape. With tapes, the thickness replaces the diameter.

[0011] In one advantageous embodiment of the invention it is envisagedthat the yarn consists of a fireproof material which is knitted, braidedor spun with itself. By way of this, staple fibers may be advantageouslydone away with by which means one further requires no expensive DREFmachine.

[0012] The knotting ability of the binding yarn as well as the lifeduration of the incandescent hood may further be improved in that thebinding yarn is textured. It has been surprisingly found out that atexturing of the binding yarn significantly contributes to an increasein the life expectation of the incandescent hoods. In trials with whichthe burnt-off incandescent hood is subjected to an impact loading or toan oscillation loading, there resulted an increase of the durability ofup to threefold with respect to incandescent hoods which were fastenedwith yarn according to the state of the art. In this context yarn is tobe understood as a ductile, one-dimensional body, thread, yarn or tape.Texturing is to be understood as various methods which increase thesmooth structureless filaments in volume. Smooth yarns are for examplecrimped in a lasting manner, and thus so-called crimp yarn, crimp twine,textured yarn, stretch yarn arises, whose extensibility is increased onaccount of its spun-yarn-like appearance.

[0013] A yarn, in particular a silicate yarn which is textured by way ofa nozzle blower method has shown to be particularly suitable.

[0014] For an improved knotting ability it is advantageous if the yarnhas an etched surface. The type of yarn is not limited; allhigh-temperature yarns with a smooth surface without exception areconsidered, such as yarns of glass fibers, carbon fibers or mineralfibers or any mixtures of these. The etching may for example, beeffected with hydrofluoric acid. A significant shrinkage of the diameteradvantageously does not take place so that the incandescent body has anincreased service life. The high-temperature yarn, e.g. silica yarnamongst others is etched in hydrofluoric acid, subsequently washed anddried.

[0015] In one advantageous alternative embodiment of the invention it isenvisaged that the yarn is enveloped by a layer of combustible material,preferably is wound around, knitted around, woven around or spun aroundby endless filaments or endless yarns.

[0016] Such a layer may be manufactured in a particularly economicalmanner if the layer consists of a plastic, preferably a polymer. Aplastic polymer or a natural polymer is added to the high-temperatureyarn and the smooth surface of the original yarn is coated with this.Monomers or pre-polymers are added to the high temperature yarn whichare subsequently polymerized so that amongst other things one mayachieve effects. Examples of such polymers are polyacrylates,polymethacrylate, casein, polyacrylnitrile, and latex, but also polymerswhich are to be indicated as high temperature polymers on account oftheir properties. The refined yarns may be manufactured with simplemeans and with various methods. This may be effected by impregnating,mechanical addition or spraying of the yarn and subsequent drying, etc.The chemical refining only slightly changes the Tex number of the rawyarn so that the disadvantages of the yarn according to the state of theart do not arise. The incandescent body manufactured with the new yarndescribed here has a greater mechanical retention ability on the burnerthan with incandescent bodies manufactured with known yarn since alsoafter the burning-away of the incandescent body, the yarn is just asfirmly connected to the burner than before the burning-away. Forchemical bonding one may also add textile additives such as softeners,surface-active substances, etc. The special yarn manufactured in thismanner may further be subjected to reviving. The applied chemicalcompound either burns without residue or the residue in its quantity isso low that it does not adversely affect the performance of theincandescent body. The possibility of coloring the yarn is of a greatsignificance. This may be effected by the addition of a dye fordissolving or a dispersion in which the chemical compound is located.

[0017] If the yarn consists of several fiber strands, preferably 2 to 3,preferably twisted fiber strands which in particular have alength-related mass of 170 Tex per fiber strand, then this may be easilyimpregnated with such plastics. The yarn treated in this manner, if itconsists of a number of filaments and possibly also stack fibers, by wayof chemical refinement becomes a compact unit and behaves like a thread,by which means the processing ability (sewing ability, cutting ability,processing by machine etc.) is simplified and improved.

[0018] In a further advantageous embodiment the yarn may have a woven,knitted or spun outer surface. By way of this surface structure producedby these processes, the friction is already reduced so much that theyarn may be easily knotted.

[0019] If the yarn consists of a mixture of fireproof materials andcombustible fibers, wherein preferably the share of fireproof fibers islarger or equal to 60 percent by volume, this already leads to thedesired increase in life expectation even if a part burns away.

[0020] By way of the measure that the diameter of the combustible fibersis designed smaller than the diameter of the fireproof fibers andpreferably the combustible fibers are arranged filling the intersticesof the fireproof fibers, the shrinkage in diameter is additionallyreduced.

[0021] The invention furthermore relates to the specified use of bindingyarn on an incandescent body, which consists of a tissue hose or bagwith at least one open end, wherein in each case a fireproof fasteningmaterial is provide for fastening the bag ends on a burner or on a shapepart for a burner of an incandescent lamp.

[0022] Such incandescent bodies consist of a substrate material which isknitted in a round manner. Viscose is generally used to which metalsalts are added. The incandescent body is usually attached with abinding yarn either directly on a burner but also firstly on apre-manufactured shape part for the burner (the shape part with thefastened incandescent body is placed onto the burner by the endconsumer) and subsequently burnt away and brought to radiate in the gasflame.

[0023] With this the substrate material burns away completely and onlythe oxide skeleton of the metal salts remain. Low mechanical loading isalready sufficient to destroy it. If now this oxide skeleton issubjected to impact and vibration, as e.g. with the transport of thelamp or with careless handling, then the incandescent body is destroyedusually at its weakest location, specifically at the burner.

[0024] For increasing the mechanical durability of the incandescent bodyon the burner the following methods are known in the state of the art.

[0025] One method lies in reinforcing the tissue at the contact locationto the burner. In order to reinforce the oxide skeleton at its contactlocation to the burner, the tissue is turned up in the region of theburner and is chemically reinforced in this region and is thus presentdouble. The tissue and the oxide skeleton remaining after theburning-away now consist of two plies which are chemically reinforced.This double-ply oxide skeleton increases the time of the intactretention of the incandescent body on the burner on exposure to knocksand impacts.

[0026] A further way lies in the selection of the binding yarn withwhich the incandescent body is bonded on the burner. A yarn is sewn intothe tissue in order to attach the incandescent body on the burner.Different burners require a different ending of the binding yarn. Withthe remaining fastening method, on production, a yarn is drawn into thefastening opening, or into the two fastening openings of theincandescent body with more or less many stitches, whereupon the endconsumer then pulls the incandescent body either on a ceramic ring or anelongate one-part or two-part burner and tightly pulls the ends of theyarn together and ties them with a knot.

[0027] For other burner types the incandescent body is drawn togetherand pre-knotted already during the production procedure, wherein thediameter of the opening remaining in this manner is prescribed exactlyto a tenth of a millimeter.

[0028] The fastening material surprisingly has an influence on thedurability of the incandescent body. The binding yarn is the most commonworldwide fastening method of the incandescent body.

[0029] By way of the fact that the binding yarn according to one or moreof the claims 1 to 11 are used for fastening an incandescent body of theabove described manner, the application duration and mechanicalstability of the incandescent body increases. In order to test themechanical durability of the incandescent body, the burnt-awayincandescent body together with the burner are attached to a joltingmachine and jolted for so long until the incandescent body is damaged.The jolt time is a measure for the control of the mechanical durabilitywith respect to knocks and impacts. The incandescent bodies manufacturedaccording to the present invention surprisingly have extended durabilityand serviceable life by more than threefold. On being subjected toknocks, impacts and vibrations the incandescent body in the context ofthe invention has a completely different nature than the conventionalincandescent body. The conventional incandescent body is destroyed inthat the oxide skeleton successively separates away from the bindingyarn until it is no longer held by this and falls down from the burner.If the incandescent body manufactured according to the invention issubjected to knocks, impact and vibration, then the oxide skeleton nolonger separates from the binding yarn and by way of this is held on theburner for a considerably longer time. This incandescent body below thefastening and specifically in the incandescent body itself is destroyedso that the durability of this is only dependent on the nature of theoxide skeleton from which the incandescent body is manufactured, andfrom the design of the burner.

[0030] The preferably textured fastening material connected to theincandescent body, if the incandescent body is subjected to knocks,impacts and vibrations, thus serves as a protective medium whichprotects the oxide skeleton from separating from the fastening material.This fastening material may be worked in as a thread for example asfollows:

[0031] a. It is worked into the incandescent body tissue with stitches(similar to how the binding yarn is sewn in).

[0032] b. In the region of the opening it is worked in around andthrough the incandescent body tissue in the manner of a loop. There maybe several loops which are continuously incorporated, or, alsoindividually and separate ones which are attached at various locationsalong the opening, and may each be individually knotted.

[0033] c. It may be incorporated into the device in a manner such thatit is suspended only on the binding medium on the inner side of theincandescent body in the region of the burner by way of the most variedof stitches (e.g. buttonhole stitch)

[0034] d. It is fastened on the inner side of the incandescent body inthe region of the burner (e.g. by way of gluing or adhering).

[0035] e. On the knitting machine in the knitting procedure of thesubstrate material (usually viscose) it is incorporated in theincandescent body tissue at least in the region of the burner.

[0036] With this, in a further embodiment of the invention it isenvisaged that the binding yarn is guided through the tissue bag forminga loop over the periphery of the tissue bag. The at least one loop orloops need not necessarily be present already in the unfastenedcondition but may be formed not until on fastening to the burner. Theloops neither need to be closed but may for example also be present as ameander.

[0037] A further increase in the durability may be achieved if thebinding yarn is led in a noosed manner around the end of the tissue bag.In this fashion the formed nooses simultaneously reinforce the tissueend. The binding yarn itself after it has been sewn in around theincandescent body according to the usual method may once again be workedin around or along the opening of the incandescent body and by way ofthis becomes a protective medium with the second turn.

[0038] The incandescent body need only be slightly modified in order toachieve the advantages according to the invention if the binding yarn isarranged in a penetrating manner at a distance to the end of the tissuebag, wherein it is fastened on the tissue bag such that on tightening itforms loops. With this design one may advantageously do away withadditional spacer bodies or threads. The binding yarn itself acts itselfas a spacer body by way of the loops being formed. For example thebinding yarn itself after it has been sewn in around the incandescentbody according to the usual methods, may once again be worked in aroundor along the opening of the incandescent body and by way of this becomesa protective medium with the second turn. Or alternatively the bindingyarn is not sewn in the incandescent body according to the usualmethods. The binding yarn in the manner of a noose is sewn in around theopening of the incandescent body so that the yarn lies therebetween inthe region of the incandescent body which faces the burner. It is at thesame time a binding medium and protective medium.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention is described by way of example by way of thedrawings.

[0040] The figures of the drawings individually represent in FIG. 1 aschematic side view of the use according to the invention, of bindingyarn on an incandescent body in the unfastened condition according to afirst embodiment example,

[0041]FIG. 2 is a plan view of the end of an incandescent body accordingto FIG. 1.

[0042]FIG. 3 is a schematic side view of the use according to theinvention, of binding yarn on an incandescent body in the unfastenedcondition according to a second embodiment example.

[0043]FIG. 4 is a plan view of the end of an incandescent body accordingto FIG. 3.

[0044]FIG. 5 is a schematic side view of the use according to theinvention, of binding yarn on an incandescent body in the unfastenedcondition according to a third embodiment example.

[0045]FIG. 6 is a plan view of the end of an incandescent body accordingto FIG. 5.

[0046]FIG. 7 is a schematic side view of the use according to theinvention, of binding yarn on an incandescent body in the unfastenedcondition according to a fourth embodiment example.

[0047]FIG. 8 is a plan view of the end of an incandescent body accordingto FIG. 7.

[0048]FIG. 9 is a schematic side view of the use according to theinvention, of binding yarn on an incandescent body in the unfastenedcondition according to a fifth embodiment example.

[0049]FIG. 10 is a plan view of the yarn according to the invention,according to a first embodiment.

[0050]FIG. 11 is a cross section through the yarn according to FIG. 10.

[0051]FIG. 12 is a view of the yarn according to the invention accordingto a second embodiment.

[0052]FIG. 13 is a cross section through the yarn according to FIG. 12.

[0053]FIG. 14 is a plan view of the yarn according to the inventionaccording to a third embodiment.

[0054]FIG. 15 is a cross section through the yarn according to FIG. 15.

[0055]FIG. 16 is a plan view of the yarn according to a furtheralternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] In FIGS. 1 and 2, 1 indicates the incandescent body which isfirstly endlessly knitted and after a separating cut has an open end 2.At a preselected distance to the end 2, a textured binding yarn 3 ispulled through the periphery of the incandescent body such that it liesalternating on the inside and outside. Bead-like fireproof bodies 4 arepulled onto the section of the textured binding yarn lying on theinside. For this purpose these bodies have corresponding bores throughwhich the textured binding yarn may be guided. This arrangement ispreferred.

[0057] In FIGS. 3 and 4 there is shown an alternative embodiment examplewith which a thread 6 acts as a protective medium. The textured bindingyarn as in the previously described embodiment example is ledalternately through the incandescent body. The thread 6 in theinner-lying regions 7 of the textured yarn 6 is led around this in theform of a noose 8 and is thus movably fastened on the binding yarn 3.The ends of the thread 6 are fixed on the incandescent body by way of aknot 10. The thread 6 forms a loop 9 on tightening the binding yarn 3.The guiding and/or the manner of the nooses 8 may reproducibly influencethe formation of the loop 9.

[0058] In FIGS. 5 and 6 there is shown a further embodiment example withwhich the thread 6 which serves as a protective medium is led in analternating manner through the incandescent body 1 around its upper end2. Loops 9 are formed on drawing the binding yarn 3 together whichenvelope the end 2 of the incandescent body 1 in the manner of abutton-hole stitch. This type has a particularly long life span.

[0059]FIGS. 7 and 8 represent one variant of the design according toFIGS. 5 and 6. In contrast to the FIGS. 5 and 6, the binding yarn is notguided through the incandescent body 1, but through the upper ends ofthe loop 9 of the thread 6 so that the fastening of the incandescentbody 1 on the burner is now effected directly by way of the thread 6.Additionally, for reinforcement of the end 2, the incandescent body isturned up so that it is two-ply in the region between the end 2 and thecut edge 11. This region may also be additionally chemically reinforcedand/or colored. The turned-up region may also be knitted of fireproofmaterial and thus represent a tissue 13 according to the invention whichassumes the protective function.

[0060]FIG. 9 represents one embodiment example with which the bindingyarn assumes the protective function as well as the binding andretaining function. In this figure the binding yarn 3 is applied doublearound the periphery of the incandescent body and led through it severaltimes in an alternating manner. On the course of a turn it is firmlyconnected to the incandescent body at several locations 12 whilst on thecourse of the second turn it penetrates the incandescent body in adisplaceable manner. On tightening the binding yarn it therefore formsloops on course with the fastening locations.

[0061] The incandescent body which is processed in the region of theburner according to the method described above by way of a texturedbinding yarn, has a considerably higher durability if it is subjected toknocks, impacts and vibrations. Incandescent body manufactured accordingto the invention in the region of the burner, alternatively totraditional processing methods, i.e. the knocking-in of the incandescentbody, may be processed without significant losses in the durability sothat the incandescent body tissue lies double on the burner and thebinding yarn is sewn through the tissue layers, is processed as follows:

[0062] a. The incandescent body tissue is turned up in the known manner,the textured binding yarn is however only sewn through one incandescentbody tissue layer of choice (depending on the nature of the burner). Thesewing of the binding medium may be carried out more quickly and simplyin this manner.

[0063] b. The incandescent body tissue is no longer turned up, and thebinding medium is only sewn through one incandescent body tissue ply.The sewing of the binding medium may be carried out more quickly andsimply.

[0064] c. The introduction of the binding medium may be carried out moresimply, more quickly and with a perfect regularity in that the bindingmedium on the knitting machine in the knitting procedure of thesubstrate material (usually viscose) from which the incandescent body ismanufactured and transversely to the knitting direction is introduced atthe location which is fastened on the burner. This binding medium whichhas been co-knitted in, is subjected without damage to the furtherprocessing of the knitted product until the finished incandescent body.The binding medium which is co-knitted in such a manner may be handledin the same manner as the binding yarn which is sewn in the traditionalway and manner with more or less many stitches, in order to attach theincandescent body onto the burner.

[0065] In FIG. 10, 3 represents the binding yarn according to theinvention which consists of a number of fireproof fibers 14 which aretwisted with one another and whose surface has been roughened by way ofan etching process. Such a yarn after the separation avoids a shrinkagein diameter and despite this may be easily knotted.

[0066] Fibers of a combustible material 15 may additionally be added iftheir share and diameter is selected such that after burning-away, thediameter loss remains below the value according to the invention, as isfor example shown as a cross section in FIG. 11.

[0067] In FIG. 13 as a cross section and in FIG. 12 as a schematic viewthere are shown the fibers 14, and if desired, combustible fibers 15embedded or encased in a matrix 16 of a polymer. This envelope onlyinsignificantly increases the diameter. Hardly any loss in diametertakes place on burning-away.

[0068]FIG. 14 shows a schematic axial section and FIG. 15 the crosssection to this according to a further alternative embodiment form withwhich a yarn of fireproof fibers 14 is surrounded by an envelope 17 ofcombustible fibers 15. According to the invention this envelope 17 ishowever designed thinner than in the state of the art. In order toproduce a suitably thin envelope the fibers 15 are spun, woven, braidedor knitted around the core, that is to say around the inner fireprooffibers 14.

[0069] However, as is shown in FIG. 16 as a schematic view, thefireproof fibers may be directly spun, woven, braided or knitted withthemselves into a yarn so that by way of the structure which arises fromthe process there arises a sufficiently rough surface 18 which makes theyarn much easier to knot and on burning-away has no diameter loss. Onemay completely do away with combustible fibers.

What is claimed is:
 1. In an asbestos-free binding yarn for fasteningincandescent bodies to burners of incandescent lamps, whose incandescentbodies after the fastening are subjected to a flame, wherein the bindingyarn consists of a fireproof material, preferably silica yarn,characterized in that the binding yarn has a diameter change of lessthan 50% of its original diameter after exposure in the flame.
 2. Abinding yarn according to claim 1, characterized in that the yarnconsists of a fireproof material which is knitted, braided or spun withitself.
 3. A binding yarn according to claim 1 or 2, characterized inthat it comprises a texturing.
 4. A binding yarn according to claim 3,characterized in that it is textured by way of a nozzle blow method. 5.A binding yarn according to one or more of the preceding claims,characterized in that it has an etched surface.
 6. A binding yarnaccording to one or more of the preceding claims, characterized in thatit is enveloped by a layer of combustible material, preferably is woundaround, knitted around, braided around or spun around by endlessfilaments or endless yarns.
 7. A binding yarn according to one or moreof the preceding claims, characterized in that the combustible layerconsists of a plastic, preferably of a polymer.
 8. A binding yarnaccording to one or more of the preceding claims, characterized in thatthe yarn consists of several, preferably 2 to 3, preferably twistedfibers which in particular have a length-related may of 170 Tex perfibre strand.
 9. A binding yarn according to one or more of thepreceding claims, characterized in that the yarn has a knitted outersurface.
 10. A binding yarn according to one or more of the precedingclaims, characterized in that the yarn consists of a mixture offireproof fibers and combustible fibers, wherein preferably the share offireproof fibers is larger or equal to 60% by volume.
 11. A binding yarnaccording to one or more of the preceding claims, characterized in thatthe diameter of the combustible fibers is less than the diameter of thefireproof fibers and preferably the combustible fibers are arrangedfilling the interstices of the fireproof fibers.
 12. The use of thebinding yarn according to one or more of the preceding claims,characterized in that it is used for an incandescent body consisting ofa tissue bag with at least one open end, for fastening the ends of thebag to a burner or to a shape part for a burner.
 13. The use of thebinding yarn according to one or more of the preceding claims,characterized in that it is used fastened on an incandescent body,guided on the periphery of its tissue bag at at least one locationforming a loop.
 14. The use of the binding yarn according to one or moreof the preceding claims, characterized in that it is used guided in anoosed manner around the end of the tissue bag of an incandescent body.